Inserting Tab into TextView when WordWrap & TabKeyAddsTab Exhibits Odd Behavior and Crashes

[YourRobotOverlord]

Pressing the Tab key in a TextView when both WordWrap and TabKeyAddsTab are set to true causes the app to crash.

To Reproduce

Steps to reproduce the behavior:

1. Run UICatalog => Text Input Controls scenario.
2. Check "Word Wrap" and "Tab Key Adds Tab"

Behavior 1:

• Press 'Ctrl+End', 'Enter', 'Tab'
• Immediate crash.

Behavior 2:

• Press 'Ctrl+End', 'Tab', 'Right', 'Right'
• Cursor moves one column at a time as if there are spaces.
• Pressing 'Backspace' or 'Delete' anywhere in these "spaces" causes immediate crash.

Behavior 3:

• Press 'Tab' in the middle of a line of text.
• 4 spaces are inserted.
• Pressing 'Delete' or 'Backspace' removes incorrect characters from the text.

All functions work correctly if Word Wrap is false

OS Information

This repros on Windows and Linux.

[BDisp]

The Tab processing is truly a disaster. I'm almost certain there were unit tests that safeguarded against some of these situations, as that's what they're for – to prevent future errors. There are different places in the code where various exceptions are thrown, depending on the procedure performed.

[BDisp]

The problem is that the tab is not preserved in wrapped lines and is replaced by spaces, so the TextView cannot draw the tab, instead drawing the existing spaces. When WordWrap is false, the TextView adjusts to the width of the tab. When WordWrap is true, the TextFormatter replaces the tab with spaces in wrapped lines, so the TextView only treats them as simple spaces, not positioning the cursor accordingly and using incorrect locations that can exceed the text width, throwing exceptions. It's possibly always been like this, I don't remember anymore.